We have developed methods to measure the hypothalamic hormones, thyrotropin releasing hormone and somatostatin by radioimmunoassay, receptor assay, and bioassay techniques. These assays will be used to study the regulation of hypothalamic hormone secretion by thyroid hormones, cold stress, and various bioactive amines. Secretion of hypothalamic hormones will be correlated with the degree of their binding to receptors on dispersed pituitary cells derived from each condition.